Currently, no fully integrated high voltage p-intrinsic-n (i.e., PIN) diode drivers exist that are capable to both sink and source high currents. High-power wide-band series-shunt PIN diode switches are specified to have low insertion loss to improve efficiency and power handling in a transmission path, and minimize a noise figure in a receive path. The PIN diode drivers supply bias currents to series PIN diodes and sink currents into an output buffer.
Shunt diodes are widely used in the PIN diode switches to improve isolation. For the wide-band switches, working down to several hundreds of megahertz, a DC blocking capacitor between the receive series diode and the shunt diode is not practical because of the physical size. Without the DC blocking capacitor, the back bias voltage used to turn off the receive series diode also directly biases the receive shunt diode in an on-state. For high-power lower-frequency applications, the back voltage can be as high as 50 volts. A high voltage power supply of the PIN diode driver provides the high currents.
To achieve the high sinking/sourcing current criteria for a high voltage PIN diode driver, a typical solution is to use discrete power metal-oxide-silicon field effect transistors (i.e., MOSFETs) as an output buffer, due to high current ratings, and a discrete or integrated gate driver to level-shift digital input controls. A large current limiting resistor with a high power rating is added between the high-side MOSFET and the output to protect the MOSFETs from high transient currents when switching states. The conventional solutions take significant printed circuit board area and are slow in terms of switching speed, typically longer than 1 microsecond.
Conventional full-bridge or half-bridge gate driver integrated circuits are sufficiently fast enough to drive the high power discrete MOSFETs. The conventional drivers have problems driving the PIN diode switches. The drivers include bootstrap capacitors in charge pumps to fully shut down the high side MOSFET. However, the charge in the bootstrap capacitor will discharge over time, thereby preventing the PIN diodes from being in the off-state for a sustained period.
It would be desirable to implement a 20V to 50V high current ASIC PIN diode driver.